Mice are capable of generating cytotoxic T cells which lyse anti-idotype bearing B cell hybridomas. Immunization with anti-idiotypic antibody is another way of generating antigen specific cytotoxic T cells. By fusing antigen specific cells with a muring T cell tumor, immortal cytotoxic T cells which survive without growth factor can be generated. These cytotoxic T hybridomas and growth factor dependent CTL will be used to investigate the development and regulation of T cell immunity. These studies involve an analysis of the control of receptor bearing tumors.